U.S. patent application number 17/605010 was filed with the patent office on 2022-07-07 for method and apparatus for friction current joining.
The applicant listed for this patent is KUKA Deutschland GmbH. Invention is credited to Andreas Burger, Stefan Habersetzer, Jorg Herrich, Andy Pham, Klaus Schneider.
Application Number | 20220212281 17/605010 |
Document ID | / |
Family ID | 1000006273141 |
Filed Date | 2022-07-07 |
United States Patent
Application |
20220212281 |
Kind Code |
A1 |
Herrich; Jorg ; et
al. |
July 7, 2022 |
Method and Apparatus for Friction Current Joining
Abstract
A method and apparatus for joining using friction and current,
wherein the friction/current joining apparatus includes a friction
device, a forging device, an electrical current source, and a
programmable controller, as well as workpiece holders for the
workpieces to be joined. The friction/current joining apparatus is
controlled such that, in a contacting phase, the workpieces are
initially moved along a process axis, and their mutually facing
joining surfaces oriented transverse to a common process axis are
brought into contact. In a grinding phase, while subjected to
contact pressure by mutual relative movement, the joining surfaces,
are ground together and made smooth. At the end of the grinding
phase, the relative frictional movement is permanently stopped and,
in a forging phase following the grinding phase, the workpieces are
pressed together, plasticized, and joined while subjected to
contact pressure on their contacting joining surfaces along the
process axis, and subjected to conductive heating with electrical
current.
Inventors: |
Herrich; Jorg; (Mering,
DE) ; Habersetzer; Stefan; (Rinnenthal, DE) ;
Schneider; Klaus; (Friedberg, DE) ; Burger;
Andreas; (Augsburg, DE) ; Pham; Andy;
(Augsburg, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KUKA Deutschland GmbH |
Augsburg |
|
DE |
|
|
Family ID: |
1000006273141 |
Appl. No.: |
17/605010 |
Filed: |
April 24, 2020 |
PCT Filed: |
April 24, 2020 |
PCT NO: |
PCT/EP2020/061466 |
371 Date: |
October 20, 2021 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B23K 2103/14 20180801;
B23K 20/129 20130101; B23K 11/02 20130101; B23K 20/121 20130101;
B23K 13/04 20130101 |
International
Class: |
B23K 20/12 20060101
B23K020/12 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 25, 2019 |
DE |
10 2019 110 664.8 |
Claims
1-24. (canceled)
25. A method for joining, using friction and current, two or more
workpieces by grinding and by conductive heating with electrical
current, the method comprising: in a contacting phase, moving the
workpieces along a process axis such that respective joining
surfaces of the workpieces facing each other and oriented
transverse to the process axis are brought into contact; prior to
or beginning with the contact of the joining surfaces, rotating the
workpieces relative to each other in directions transverse to the
process axis or about the process axis; in a grinding phase that
begins with the contact of the joining surfaces, grinding the
workpieces against each other, subjected to contact pressure, due
to the mutual relative movement at the joining surfaces such that
the joining surfaces are made smooth; at the end of the grinding
phase, stopping the relative grinding movement of the workpieces;
and in a forging phase directly following the grinding phase,
forging, plasticizing, and joining the workpieces at their
contacting joining surfaces, subjected to contact pressure along
the process axis and subjected to immediate and continuous
conductive heating by electric current.
26. The method of claim 25, wherein the plasticizing, heating and
joining of the workpieces subjected to contact pressure is effected
at least primarily by the conductive electrical heating in the
forging phase.
27. The method of claim 25, wherein the grinding phase is performed
substantially without subjecting the workpieces to pulsed
electrical current.
28. The method of claim 25, further comprising: subjecting the
workpieces to a relatively low electrical current density in the
grinding phase; and subjecting the workpieces to a significantly
increased electrical current density in the forging phase, compared
to the current density in the grinding phase.
29. The method of claim 25, further comprising subjecting the
workpieces to an adjusted, constant direct current.
30. The method of claim 25, wherein the workpieces are subjected to
a current density of between about 30 to 50 A/mm.sup.2 in the
forging phase.
31. The method of claim 25, wherein: the workpieces are subjected
to the electrical current only at the end of the grinding phase; or
the workpieces are subjected to the electrical current only after
the end of the grinding phase and the frictional relative
movement.
32. The method of claim 25, wherein the workpieces are subjected to
the electrical current when they are at a standstill.
33. The method of claim 25, wherein, the workpieces are subjected,
on the joining surfaces, to essentially the same contact pressure
during the grinding phase and the forging phase.
34. The method of claim 25, wherein the workpieces are pressed
together with a contact pressure of 125 MPa or less.
35. The method of claim 25, further comprising: detecting one or
more physical parameters associated with the workpieces during the
joining process; and controlling at least one of the contacting,
grinding, or forging phases according to the one or more detected
physical parameters.
36. The method of claim 25, further comprising at least one of:
electrically preheating the workpieces before the joining phase; or
electrically reheating the workpieces after the joining phase.
37. The method of claim 25, further comprising one of:
demagnetizing an apparatus used for friction/current joining the
workpieces; or demagnetizing an apparatus used for friction/current
joining the workpieces and demagnetizing the workpieces.
38. The method of claim 37, wherein the demagnetization takes place
with a direct-current demagnetization having a reverse polarity
relative to the heating current for conductive heating.
39. The method of claim 38, wherein the direct-current
demagnetization is pulsed.
40. An apparatus for joining, using friction and current, two or
more workpieces by grinding and by conductive heating with
electrical current, the apparatus comprising: workpiece holders for
supporting the workpieces to be joined; a friction device; a
forging device; an electrical current source; and a programmable
controller having programming code designed to control the friction
device, the forging device, and the electrical current source to
carry out the method of claim 25.
41. The apparatus of claim 40, wherein: the electrical current
source is programmable, and is connected to the workpieces in an
electrically conductive manner via current connections; the current
connections are arranged on at least one of the workpieces or the
workpiece holders; and each current connection has one or more
electrodes.
42. The apparatus of claim 40, wherein: the electrical current
source is designed as a direct-current current source with a
constant current control for exact compliance with
program-controlled electrical process currents; and the electrical
current source comprises a controllable or adjustable electrical
converter.
43. The apparatus of claim 40, wherein the forging device is
designed to bring the workpieces being joined from an initially
distant loading position along the process axis into mutual contact
at their joining surfaces, and to generate a controllable contact
force.
44. The apparatus of claim 40, wherein: the friction device
comprises a machine head with a rotating drive for one of the
workpiece holders; the other workpiece holder being arranged on a
counter holder; and the machine head and the counter holder are
mounted on a machine frame for movement relative to each other
along the process axis.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a national phase application under 35
U.S.C. .sctn. 371 of International Patent Application No.
PCT/EP2020/061466, filed Apr. 24, 2020 (pending), which claims the
benefit of priority to German Patent Application No. DE 10 2019 110
664.8, filed Apr. 25, 2019, the disclosures of which are
incorporated by reference herein in their entirety.
TECHNICAL FIELD
[0002] The invention relates to a method and an apparatus for
joining two or more workpieces by friction and current.
BACKGROUND
[0003] It is known from practice to join two or more workpieces by
friction welding, the workpieces being brought into contact with
each other at their joining surfaces, and briefly ground together
with relative mutual movement under low contact pressure. In a
subsequent friction phase with significantly increased contact
pressure and continuing relative movement, the contacting joining
surfaces of the workpieces are plasticized by the frictional heat.
Subsequently, they are pressed against each other by a high forging
pressure in a forging phase. In the grinding phase and the forging
phase, the plasticized material is laterally displaced in the
joining zone between the joining surfaces of the workpieces,
forming a bulge, and the workpiece is also shortened. The
conventional friction welding process can lead to fiber deflections
and hardening in the joining zone.
[0004] DE 299 22 396 U1 teaches such a friction welding with a
grinding and friction phase, which is designed for critical
workpieces with very different melting behavior to be friction
welded. With an additional heating device, in addition to the
frictional melting heat, additional heating energy is applied to
one of the workpieces being friction-welded, in a targeted manner,
or with a stronger effect on one side, in order to compensate for
the different melting behavior and to additionally heat the
workpiece, which is more difficult to melt. The additional heating
device is preferably an induction heater, wherein modifications
with hot air, an open flame, or with a resistance heater, etc.
applied to a workpiece, are possible.
[0005] It is also known from practice to electrically-inductively
preheat the workpieces being welded during friction welding, or to
reheat the welded part electrically after the joining process. DE
10 2016 217 024 A1 and WO 2010/054627 A1 teach inductive heating of
the workpieces during the friction phase, and the relative movement
of the workpieces to produce friction.
[0006] DE 693 13 131 T2 relates to the abrasion welding of
workpieces that are clamped one inside the other, and thereby moved
relative to each other in the insertion direction, giving rise to
abrasion at the contact points or clamping points, and
amplification of the abrasion during the relative movement by an
electrical heater. In the process, by welding the abraded
particles, an abrasion bond with a strong diffusion bond is
created.
SUMMARY
[0007] It is the object of the present invention to create an
improved joining technique.
[0008] The claimed joining technology--that is, the method and the
apparatus for joining using friction and current--has various
advantages.
[0009] According to the claims, the workpieces are joined by
friction and current in a multi-step process which is divided into
a contacting phase, a subsequent grinding phase, and an immediately
following forging phase with electrical conductive heating.
[0010] The additional friction phase with frictional relative
movement under high contact pressure and deep plasticization of the
workpieces due to the resulting frictional heat, as is present in
conventional friction welding, is omitted. In the invention, the
workpieces are instead heated and plasticized by the conductive
electrical heating. This also eliminates the high torque peaks when
the frictional relative movement is halted, which produce high
mechanical stress on a conventional friction welding machine.
[0011] The process can begin with an upstream calibration in which
the workpieces are brought into contact during a position detection
and zero point calibration, and then are moved apart again, with a
distance measurement. After this, the contacting phase begins. In
the friction/current joining process, a path control or path
regulation is preferably used to set the desired length of the
joined prefabricated part.
[0012] In the contacting phase, the joining surfaces of the
workpieces being joined, facing each other, are brought closer to
each other, and are brought into contact. This can be done along a
common process axis or machine axis. The joining surfaces are
oriented transverse, in particular perpendicular, to the process
axis. This axis is preferably arranged horizontally and has a
predominantly horizontal directional component.
[0013] In the grinding phase, the contacting joining surfaces are
exclusively ground and made smooth while subjected to contact
pressure by mutual relative movement. The mutual relative movement
takes place transverse to the process axis. The joining surfaces
can be made smooth, mutually adapted, and brought into contact over
the entire surface. This has advantages for an improved flow of
current. The frictional energy and heat introduced in the grinding
phase only serve to smooth the contacting joining surfaces. It is
not sufficient to plasticize and melt the adjacent workpiece
regions.
[0014] The contact pressure can act along the process axis. The
frictional relative movement is preferably a rotary movement around
the process axis, which can take place continuously or in an
oscillating manner. The grinding phase begins with the contacting
of the joining surfaces. The relative movement of the workpieces
can start before contact is made, with workpieces that are still
distant. In the grinding phase, defects in shape, bevel cuts, dirt,
oil deposits and the like can be removed from the joining
surfaces.
[0015] The workpieces can each have a plurality of joining
surfaces. Due to the grinding, all contacting joining surfaces can
be made to conform to each other, and can contact each other over
the entire, flat surface for the subsequent joining. This is
favorable for the uniform heating of all joining surfaces during
friction/current joining with electrical conductive heating.
[0016] At the end of the grinding phase, the workpieces or the
contacting joining surfaces are brought to a motionless state. The
termination of the frictional relative movement is preferably
permanent, that is to say the frictional relative movement is not
resumed in the immediately following forging phase.
[0017] In the forging phase, the workpieces or the contacting
joining surfaces are pressed together, plasticized and joined
subjected to contact pressure, with conductive heating with
electrical current. The contact pressure acts along the process
axis. The electrical current is preferably a regulated constant
current. The use of direct current is favorable. The current
density can advantageously be, for example, 30-50 A/mm.sup.2.
[0018] The workpieces are made of an electrically conductive
material. Ferrous metals, in particular steels or cast ferrous
materials, are particularly suitable and preferred for
frictional/current joining. Titanium materials or nickel-based
alloys are also advantageously suitable.
[0019] In the forging phase, the axial contact pressure can be the
same as in the grinding phase or, preferably, it can be increased
slightly. The conductive electrical heating is present immediately
at the beginning of the forging phase, and continues through the
forging phase.
[0020] In an advantageous embodiment, the electrical voltage or
current is only switched on after the frictional relative movement
has ended, in particular in the case of stationary, contacting
workpieces that are subjected to contact pressure. The plasticizing
and joining of the workpieces subjected to contact pressure takes
place primarily through the conductive heating in the forging
phase. The heat required for joining is substantially applied by
means of electrical conductive heating. During the forging phase,
it is advantageous if the workpieces do not perform any frictional
movement relative to each other.
[0021] The claimed friction/current joining technique offers high
reproducibility and quality of the joining technique and of the
manufactured joined parts. The same amount of energy can always be
converted and used for the joining process. The even flow of
current through the participating joining surfaces, and the even
heating of these joining surface regions, ensure high and even
joint quality. The contact surfaces and the adjacent workpiece
regions are plasticized by the heat of the current. The usual
fluctuations in heating due to corrosion, roughness, lubricating
film etc. on the joining surfaces in friction welding can be
avoided.
[0022] With the known inductive heating of the workpieces, the same
qualities cannot be achieved as with friction/current joining
according to the invention with conductive electrical heating.
Induction heating is also more inefficient.
[0023] Compared to other joining techniques, the claimed
friction/current joining technique succeeds with less workpiece
shortening, and enables improved and more precise compliance with
the dimensional specifications for the joined part or welded part.
With friction/current joining, length control for the joined part
or welded part can be carried out more easily and more
precisely.
[0024] In addition, lower forces and torques are required for
positioning, in particular rotational positioning, of the
workpieces during joining. The positioning can be adjusted easily
and precisely during the grinding, and does not have to be changed
during the subsequent joining with forging and conductive heating.
Any position specifications, for example a rotational position of
the workpieces on the finished joined or welded part, can be
adhered to exactly. A bulge formation on the joining zone of the
workpieces can be avoided or at least significantly reduced
compared to friction welding.
[0025] With friction/current joining, thanks to the conductive
electrical heating of the workpieces, the temperatures in the
joining zone and in the other workpiece regions can be better
monitored and controlled and, if necessary, adjusted. As part of a
temperature detection, the friction/current joining process for
metals can be optimized using its temperature-dependent
transformation and phase behavior, as well as the associated TTT
diagrams. The desired joining structure can be achieved in a
targeted, safe and reproducible manner.
[0026] The temperature can be detected directly or indirectly, for
example via the electrical resistance R, for example for the
purposes of process monitoring. The electrical resistance R can
also be used to control or regulate the grinding process, for
example with a low current density. This results in advantages for
cycle time savings, reproducibility and process reliability, and
quality assurance.
[0027] The claimed friction/current joining technique achieves
shorter process times and a more economical use of energy compared
to the prior art. The conductive heating with electrical current of
the workpieces being joined enables the workpieces to be heated
evenly, quickly and precisely. In contrast to conventional friction
welding, the temperature rise or heating takes place not only in a
narrowly bounded area at the joining zone, but also in the
adjoining other workpiece regions through which the current flows.
The heating zone is considerably widened in the case of
friction/current joining. The heating can take place uniformly over
the cross-section of the joining surfaces of the workpieces. In
this way, the hardening of the joined part in the joining zone,
which is usual in conventional friction welding, can be prevented
or at least reduced.
[0028] Thanks to the uniform conductive electrical heating of the
workpieces being joined, a contact pressure in the forging phase
that is significantly lower than in conventional friction welding
is sufficient for the friction/current joining process. It can be
125 MPa, in particular 100 MPa, or less--compared to up to 250 MPa
as is customary in conventional friction welding, based, for
example, on a pairing of two workpieces made of steel. In the
claimed friction/current joining, the axial contact pressure in the
grinding phase, and optionally in the forging phase, can be, for
example, 20-40 MPa. The contact pressure is calculated as the
contact pressure per surface area of the contacting joining
surfaces of the workpieces.
[0029] The lower contact and forging pressure prevents or reduces
upturned fiber imperfections in the workpiece material at the
joining zone. A short grinding time with reduced contact pressure
is also beneficial for this purpose. Furthermore, a homogeneous
structure can be achieved. The approach results in advantages for
improving and increasing strength, in particular fatigue strength,
in the region of the joining zone, and for protection against
corrosion. The homogeneous structure is less susceptible to
corrosion. Furthermore, rolled-up beads and their corrosion
problems can be avoided.
[0030] In the claimed friction/current joining, the friction phase
included in conventional friction welding, with relative movement
of the workpieces subjected to high contact pressure and friction
heating of the workpieces, is omitted. The claimed friction/current
joining technique achieves significantly lower forces or torques
with a significantly lower energy requirement. Flywheels used for
inertia friction welding are not necessary. On the one hand, this
enables a reduction in the dimensions of the friction/current
joining apparatus compared to conventional friction welding
machines or, with the dimensions remaining the same, the joining of
significantly larger workpieces and larger joining surfaces.
[0031] In the claimed friction/current joining technique, the
grinding phase at low contact pressure serves to smooth the
contacting joining surfaces. Unevenness is eliminated, and the
effective contact areas on the contact surfaces are enlarged and
evened out. This is favorable for a full-area and uniform flow of
current on the contacting joining surfaces, and for a
correspondingly uniform heating of the workpieces. The
aforementioned low contact pressure and a very short grinding time
are sufficient for the grinding process. This can be one second or
less, by way of example. Depending on the workpiece and material
pairing, it can also be a little longer.
[0032] In the grinding phase, it is beneficial not to apply
electrical current to the workpieces. Alternatively, a brief and
pulsed application of electrical current at low current density is
possible. By concentrating current at the tips of uneven regions in
the joining surfaces, the removal of these uneven regions can be
facilitated. The thermal energy introduced is very low in the cases
mentioned. This is advantageous for keeping the drive energy
required for the grinding and for the relative movement of the
workpieces low. Unevenness on the joining surfaces can be made
smooth more easily and more quickly, and friction-increasing
adhesion phenomena on the contacting joining surfaces can be
avoided or at least significantly reduced.
[0033] The plasticization of the workpieces at the joining zone and
the formation of the joining connection take place in the claimed
friction/current joining technique essentially or only during the
forging phase, and due to the effect of the electric current and
the conductive heating. The plasticization and the conductive
heating are uniform thanks to the aforementioned smoothing in the
grinding phase, and can take place over the entire area of the
joining surface. The heating not only occurs locally at the joining
zone, but extends over a large axial length of the adjacent
workpiece regions.
[0034] The frictional relative movement of the workpieces on their
contacting joining surfaces can be ended after the grinding phase.
The longer friction phase that is common in normal friction welding
is therefore no longer necessary. The subsequent forging phase can
take place at the end or after the end of the frictional relative
movement. A frictional relative movement of the workpieces is
preferably also dispensed with in the further course of the forging
phase.
[0035] The application of current to the workpieces and their
conductive heating takes place primarily during the forging phase.
The application of the electrical voltage and/or the flow of
current can take place at the end or after the end of the grinding
phase and/or the grinding relative movement. The electrical current
can be switched off at the end of the forging phase, and the
contact pressure is released at the same time. The current can also
be switched off before the end of the forging phase and of the
contact pressure.
[0036] The workpieces can be moved continuously, rotating and/or
oscillating, on their contacting joining surfaces relative to each
other in the grinding phase. A rotary movement is particularly
favorable for smoothing and for exact and definable adaptation of
the joining surfaces. An oscillating relative movement can
alternatively or additionally be translational. Furthermore, it is
favorable if the contacting movement and the pressure, as well as
the forging force, take place along a forging axis or machine axis
of a friction/current joining apparatus. The process axis can be
the forging axis.
[0037] The current source and the current supply to the workpieces
being joined or to the apparatus parts connected to the workpieces
being joined, in particular the workpiece holders, can be designed
in any suitable manner. The current for the conductive electrical
heating of the workpieces in the forging phase can enter the
circuit in the rest position of the workpieces and/or of the
workpiece holders. It can also enter during the grinding phase at
low speed, for example.
[0038] For the preferably rotating workpiece holder, electrodes are
advantageous that can be moved during the stationary state, for
example in the form of jaws or permanent electrical sliding
contacts--for example, brushes. The other workpiece holder can be
permanently connected to the current supply in an electrically
conductive manner. To compensate for the axial workpiece feed, the
current supply can be equipped with an elastic line, or can be
designed to be able to follow in some other way.
[0039] A programmable, and also controllable and adjustable,
current source is expedient. A current source for direct current
with a constant current regulation for exact compliance with the
program-controlled electrical process currents is of particular
advantage.
[0040] In addition, it is advantageous if medium-frequency
technology components are used for the current source and the
current-carrying parts. Such a medium-frequency technology
operating at 1,000 Hz, for example, is standardized and
inexpensive. There are also advantages in terms of occupational
safety and electromagnetic compatibility, so-called EMC.
[0041] The voltages at the current-carrying points, in particular
at the electrodes, can be low. They can be in the range of, for
example, 5-30 V direct current. This is an advantage for accident
prevention and for safety.
[0042] A demagnetization device can be provided for any
magnetizations that may occur on the friction/current joining
apparatus and, if applicable, on the workpieces. This can be
designed and act in different ways. During conductive heating with
direct current, for example, it can generate an optionally-pulsed
demagnetizing current with opposite polarity. The demagnetizing
current is a lower current than the heating current, and is
sufficient to achieve the coercive field strength of the magnetized
material. The demagnetization with, for example, one or a plurality
of current pulses can take place during the forging phase.
[0043] It is possible if necessary, in addition to the claimed
friction/current joining technique, to reheat the workpieces
electrically after joining. This can also be done by conductive
heating, and/or alternatively or additionally by inductive heating.
Electrical preheating before joining is also possible, but less
desirable.
[0044] Particular advantages of the claimed friction/current
joining technique relate to the homogeneity and the uniform flow of
current as well as the uniform heating of the applied joining
surfaces during conductive heating. The uniform heating over the
surface or the diameter leads to a corresponding uniformity of
strength and hardness. Further advantages relate to workpieces with
a plurality of joining surfaces, which can be joined particularly
advantageously by friction current. In rotary friction welding, due
to the movement, the heating is not uniform. It is greater at the
outer edge of the workpiece than in the inner region.
[0045] In addition, workpieces made of the same or different
electrically conductive materials can advantageously be joined by
friction current. These can be, for example, different metals or
other identical or different material combinations, for example
steel with an iron-containing cast material. The conductive heating
saves a great deal of process time and workpiece material compared
to conventional friction welding technology. In addition, the
structural properties can be significantly improved. In the
friction/current joining of workpieces with different thicknesses,
special advantages result at the joining surfaces, in particular
with relatively thin-walled pipes.
[0046] Another benefit of the claimed friction/current joining
technique is based on reducing the axial heat dissipation from the
joining zone. In conventional friction welding, the axial
temperature gradient and heat dissipation are high. Thanks to the
uniform conductive heating, this can be significantly reduced with
friction/current joining. The unfavorable structural changes of, in
particular, metallic workpieces associated with a strong
temperature gradient can be avoided or at least significantly
reduced with friction/current joining.
[0047] With friction/current joining, the uniform conductive
electrical heating introduces sufficient heat into the workpieces
and the resulting joined part, which is advantageous for the stable
and manageable joining process that can be adapted to special
material requirements, in particular structural specifications. In
addition, any bead at the joining zone can be removed more easily
and with improved qualitative results.
[0048] With the claimed friction/current joining technique,
difficult workpiece materials, in particular chromium-containing
and/or manganese-containing steels or the like, can also be joined
safely and reliably, even if they are normally not possible to
weld, or can only be welded with great difficulty. This applies in
particular to steels containing chromium, such as 102 Cr 6 and the
like. Other critical materials--for example, brittle, in particular
cold-brittle, sintered materials, and also cast materials, as well
as material combinations which are unequal and problematic with
regard to thermal behavior--can also be connected well and at high
quality with friction and current. Light metals can also be
frictionally joined to each other.
[0049] Another particular advantage is the already mentioned
prevention or reduction of hardening in the material structure at
the joining zone. With the claimed friction/current joining,
viscoplastic and ductile joining and connection regions on the
joined part can be achieved. Even critical materials, such as
chromium-containing steels, show flexurally elastic properties at
the joint area, in contrast to the embrittlement and loss of
ductility that are common in conventional friction welding. By
making the material structure more uniform at the joining region
with friction/current joining, internal notch stresses and the
resulting sensitivity to corrosion are also avoided, or at least
significantly reduced.
[0050] The above and other objects and advantages of the present
invention shall be made apparent from the accompanying drawings and
the description thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
[0051] The accompanying drawings, which are incorporated in and
constitute a part of this specification, illustrate exemplary
embodiments of the invention and, together with a general
description of the invention given above, and the detailed
description given below, serve to explain the principles of the
invention.
[0052] FIG. 1 depicts a friction/current joining apparatus in a
schematic side view,
[0053] FIGS. 2 to 5 illustrate a sequence of the joining process on
two workpieces in several steps,
[0054] FIG. 6 is a schematic diagram with profiles of contact
pressure, relative speed of movement, and electrical current over
time,
[0055] FIGS. 7 to 10 depict an exemplary a current supply and its
parts in different views, and
[0056] FIGS. 11 and 12 schematically illustrate an exemplary
degaussing device in two variants.
DETAILED DESCRIPTION
[0057] The invention relates to a method and to an apparatus (1)
for joining using friction and current of two or more workpieces
(2, 3). The invention also relates to a joined part (6) produced
from the workpieces (2, 3) using the claimed method.
[0058] The workpieces (2, 3) can consist of the same or different
electrically conductive materials. In particular, they can be
formed from the same or different metals. These can be, for
example, iron-containing steels or cast materials, titanium or
nickel-based alloys, or the like. In particular, one or more
workpieces (2, 3) can consist of steels containing chromium and
possibly manganese, for example 102 Cr 6, which are critical for
welding.
[0059] The workpieces (2, 3) can have different shapes and, in
particular, cross-sectional shapes. They can be designed as hollow
bodies, in particular as tubes, or made of solid material. The
workpieces (2, 3) have mutually facing joining surfaces (4, 5), in
particular end faces, on which the joining connection is made. One
or more joining surfaces (4, 5) can be arranged on each work piece
(2, 3). Elongated workpiece shapes are favorable.
[0060] In the embodiment shown, two workpieces (2, 3) are joined to
each other with friction and current. The friction/current joining
apparatus (1) used for this can be designed, for example, as a
so-called single-head machine. Alternatively, it is possible to
join three or more workpieces (2, 3) in one set-up at the same
time, or one after the other. A so-called double-head machine or a
double single-head machine, for example, can be used for this
purpose. In FIG. 1, the workpieces (2, 3) are shown in the already
joined state as a joined part (6).
[0061] The friction/current joining apparatus (1) shown in FIG. 1
has a friction device (7) and a forging device (8), as well as a
machine frame (9) and an electrical current source (16). The
machine frame (9) is designed, for example, as a machine bed on
which the friction device (7) and the forging device (8) are
arranged. The electrical current source (16) can be accommodated in
or on the machine frame (9), in particular the machine bed.
[0062] With the friction device (7), the workpieces (2, 3) being
joined can be moved relative to each other in the manner explained
below, subjected to contact pressure and in frictional contact.
With the forging device (8), mutual infeed and contacting of the
workpieces (2, 3) can take place. In addition, the contact pressure
of the contacting workpieces (2, 3) used for joining using friction
and current can be applied therewith. Said infeed and the
application of the contact force or the contact pressure can take
place along a preferably horizontal axis (10). This can be a
so-called machine axis or process axis, and/or a joining axis or
forging axis. In the embodiment shown, the joining surfaces (4, 5)
are aligned perpendicular to the axis (10).
[0063] The friction/current joining apparatus (1) has workpiece
holders (14, 15) for holding one or more workpieces (2, 3) being
joined. The workpiece holders (14, 15) are designed, for example,
as manually or mechanically operated chucks. These can in
particular be so-called center clamping vices.
[0064] The forging device (8) brings the workpieces (2, 3) to be
joined from an initially remote loading position, as shown in FIG.
2, into mutual contact on their joining surfaces (4, 5), and
generates a controllable and preferably adjustable contact force
(F). This acts, for example, in the direction of the axis (10). The
magnitude of the contact force (F) can depend on the size of the
surfaces being joined (4, 5), and the contact pressure acting
there. In the embodiment, the contact pressure is approximately 25
MPa.
[0065] The workpieces (2, 3) in contact are moved, in particular
rotated, relative to each other by the friction device (7).
[0066] During the relative movement, one or more of the workpieces
(2, 3) being joined are moved. In the embodiment shown, the left
workpiece (2) is moved relative to the right workpiece (3). One
workpiece holder (14) for the workpiece (2) is movable, and the
other workpiece holder (15) for the workpiece (3) is stationary.
The relative movement is a rotating movement around the preferably
central axis (10). This is also the central longitudinal axis of
the workpieces (2, 3), for example. The rotary movement can be
revolving or reversing or oscillating. This relative movement can
begin before or when contact is made. The relative movement can
also take place transverse to the axis (10). Said transverse
orientation includes right-angled and oblique orientations.
[0067] The friction device (7) has a machine head (11) with a drive
(12) for the associated workpiece holder (14). In the case of the
rotating relative movement, this can be a spindle drive with which
a spindle, which is coupled to the workpiece holder in a
rotationally fixed manner, is driven to rotate about the axis (10).
The machine head (11) can be arranged rigidly or movably on the
machine frame (9). In particular, it can be mounted on the machine
frame (9) so that it can be displaced or moved along the axis (10)
and, if necessary, can be locked.
[0068] The other workpiece holder (15) is arranged on a
counter-holder (13), which can also be arranged rigidly or movably,
in particular movable along the axis (10) and, if necessary,
lockable on the machine frame (9). The counter holder (13) can be
designed, for example, as a slide with a clamping or indexing
device.
[0069] In the embodiment shown, the counter holder (13) is advanced
by the forging device (8) to the machine head (11) and to the
workpiece (2) held there. This is a linear infeed movement,
symbolized by arrows. The forging device (8) has a forging drive
(19) for this purpose. In the embodiment shown, this can be, for
example, a fluidic, preferably hydraulic, cylinder or a motor drive
with an electric motor or a hydraulic motor. In the embodiment
shown, the forging drive develops compressive forces (F) and, with
an output element (20), such as a piston rod, pushes the workpiece
holder (15) and the counter holder (13) towards the machine head
(11). For this purpose, the forging drive (19) is arranged and
supported in a stationary manner on the machine frame (9), at least
for the infeed function. The forging force and the forging
pressure, as well as the infeed process, act along the axis
(10).
[0070] In another embodiment, not shown, a forging drive can be
arranged on the machine head (12). It can, for example, develop
tensile forces and can pull the counter holder (13) along the axis
(10) towards the machine head (11).
[0071] The current source (16) is connected in an electrically
conductive manner to the workpieces (2, 3) via current connections
(17, 18). The current connections (17, 18) can be designed in any
suitable manner. The current connections (17, 18) can be connected
to the workpieces (2, 3) directly or indirectly, for example via
the work piece receptacles (14, 15), in an electrically conductive
manner.
[0072] One current connection (18) is arranged on the, for example,
electrically conductive, in particular metallic, workpiece holder
(15) of the counter holder (13). This is, for example,
non-rotatably arranged and is moved axially by the forging drive
(19). The other current connection (17) is arranged on the, for
example, moving and also electrically conductive, in particular
metallic, workpiece holder (14) of the machine head (11).
[0073] The current connections (17, 18) can each have one or more
electrodes (28, 28', 29, 29'). These can be designed differently
from each other. The current connection (17) on the moving
workpiece holder (14) can, for example, have a plurality of
electrodes (28) in the form of slip ring transmitters or the like,
which are arranged on the circumference of the workpiece holder
(14), rotating around the axis (10) and at least partially
circular. The electrodes (28) or slip ring transmitters are
connected in an electrically conductive manner to the current
source (16) via one or more lines (30) and to the workpiece holder
(14) via slip rings, brushes or the like.
[0074] The current connection (18) on the workpiece holder (15) of
the counter holder (13) can be connected in an electrically
conductive manner to the optionally movable clamping elements of
the workpiece holder (15). The clamping elements can, for example,
form the electrode(s) (29). The current connection (18) is
connected to the current source (16) via one or more lines
(32).
[0075] The electrical current source (16) can be designed in any
suitable manner. It has a programmable controller (24). The current
source (16) can be connected on the input side to a current supply,
in particular to a local alternating current network. On the output
side, it emits a current, preferably direct current, to the
workpieces (2, 3) via the current connections (17, 18). The
electric current flows through the contacting workpieces (2, 3) in
the direction of the axis (10), and conductively heats them.
[0076] The current source (16) is designed as a programmable and
controllable, and preferably adjustable current source, in
particular a direct current source. It has a constant current
controller with which the controlled currents can be kept constant.
The current source (16) can be controlled via one or more current
programs. It works with low voltages of, for example, approx. 10 V.
The current source (16) works, for example, with medium frequency
technology of, for example, 1,000 Hz. The current delivered can be
100 kA or more. The current output depends on the size of the
joining surfaces (4, 5). The current density can be, for example,
25 to 35 A/mm.sup.2 or less.
[0077] The current source (16) can have one or more controllable or
adjustable electrical converters (26) which, for example, output a
preferably constant alternating current with a frequency of 1,000
Hz, for example. The current source (16) can also have one or more
electrical transformers (27) in addition to, for example,
integrated rectifiers, which can optionally be arranged closer to
the workpieces (2, 3). FIGS. 1 and 7 show this arrangement.
[0078] The friction/current joining apparatus (1) can have a
detection device (25) for the detection of physical parameters in
the joining process on one or more workpieces (2, 3), or at another
location. The detection device (25) can contain one or more sensors
for one or more physical parameters. In the embodiment shown, the
detection device (25) detects the temperature, by way of example,
directly on one or both workpieces (2, 3) in the joining
process.
[0079] Alternatively or additionally, voltage U and current I can
be detected in the process, and the electrical resistance R can be
derived from this as a process variable. The resistance R can also
be detected in other ways. The electrical resistance R allows a
direct conclusion about the mean temperature or the amount of heat
applied. This can be used for in-process monitoring. On the other
hand, when grinding at low current density, the resistor R can be
triggered in order to automatically control the duration or the end
of the grinding.
[0080] In the case of metallic workpieces, the transformation and
phase behavior of the material, and the structure formation depend
on the temperature and possibly on the change in temperature, in
particular on the cooling rate. The heating and, in particular,
cooling of the materials being joined and the desired phase and
structure formation caused by the conductive heat can be precisely
controlled and adjusted as required via the detected temperature
and its change in magnitude and change over time. The sensor system
for temperature detection can be designed in any suitable manner,
for example as an infrared sensor, thermal imaging camera or the
like.
[0081] The detection device (25), which is only shown
schematically, can have one or more additional sensors. This can
be, for example, a distance meter for detecting a workpiece
shortening during the friction/current joining, a travel of the
counter holder, (13) or the like. Other sensors can detect, for
example, surface properties of the workpieces (2, 3) being joined,
the position, orientation and size of a heating region (22) on the
workpieces (2, 3), a pressure on the joining surfaces (4, 5),
workpiece deformation, in particular the formation of a bead (23)
at the joining zone (21), or the like.
[0082] FIGS. 2 to 5 illustrate an exemplary sequence of the
friction/current joining process in several steps. In FIG. 6, the
curves of the contact pressure (p), the electrical current (I) and
the speed (v) of the relative movement, in particular the
rotational speed or rotary speed of the rotating workpiece holder
(14) occurring during the friction/current joining process, are
shown in an abbreviated diagram (t) as a function of time. A
contacting phase (a), a grinding phase (b) and a forging phase (c)
are also shown. The phase transitions are marked with I and II, and
the end of the forging phase (c) is marked with III.
[0083] The graphs shown for (p), (I) and (v) can vary. In
particular, the magnitude and the profile of the current (I) can be
changed for targeted control and, if necessary, regulation of the
temperature and of the structure formation on the workpieces (2,
3). This can be done, for example, by means of a current
program.
[0084] FIG. 2 shows the starting position or loading position in
which the workpieces (2, 3) are inserted into their respective
workpiece receptacles (14, 15), and are spaced from each other in
the direction of the axis (10). The workpieces (2, 3) are then
brought into physical contact at their end-face joining surfaces
(4, 5). The workpiece (3) is advanced along the axis (10) by the
forging device (8), and a contact force (F) is applied to it when
the workpieces are in contact. The so-called contacting phase (a)
is shown in FIG. 2. A calibration phase mentioned at the beginning
can take place beforehand. A distance measurement is carried out
during the advancing movement. The friction/current joining process
can be operated with a path control or path regulation of the
advancing movement, and with a length control based on this for the
shortening of the workpiece.
[0085] In this contact position, the rotating frictional relative
movement symbolized by an arrow is started. FIG. 3 shows this
grinding phase (b) and its beginning I.
[0086] The workpiece (2) is rotated by the spindle drive (12) about
the axis (10), relative to the stationary or fixed workpiece (3).
In this case, an initially lower axial contact pressure (p) is
applied, in accordance with FIG. 6. The rotational movement can be
started when the workpieces (2, 3) are in contact, or beforehand.
FIG. 6 shows the start beforehand.
[0087] In the grinding phase (b), the current source (16) is
switched off, by way of example. During the grinding, the end-face
joining surfaces (4, 5) are made smooth in the frictional contact,
with unevenness being removed and the joining surfaces (4, 5) being
made smooth and mutually adapted to each other.
[0088] The duration of the grinding phase (b) is very short. It is,
by way of example, 1 second or less. In the grinding phase (b),
little heat is generated in the joining zone (21) where the joining
surfaces (4, 5) contact each other. The heating region (22) shown
in dashed lines is small when viewed in the axial direction.
[0089] FIG. 6 illustrates a variant in the griding phase (b), in
which the current source (16) is switched on and emits one or more
short-term current pulses. Such a current pulse is shown in dashed
lines in FIG. 6.
[0090] FIGS. 4 and 5 illustrate the immediately subsequent forging
phase (c). At the end of the grinding phase (b), the relative
movement of the workpieces (2, 3) is ended, in accordance with FIG.
4. This is symbolized by the dashed movement arrow. The workpieces
(2, 3) remain in their relative position assumed at the end of the
grinding phase (b), for example according to FIG. 5, in the further
course of the forging phase (c). In this fixed relative position,
the workpieces (2, 3) can be positioned in a defined rotational
position with respect to each other.
[0091] During the deceleration phase or starting from and/or after
the workpieces (2, 3)--still in contact--come to a stop, the
contact force (F) and the contact pressure acting on the joining
surfaces (4, 5) are kept the same or increased. FIG. 6 shows this
behavior at the point and/or at time II.
[0092] In the grinding phase (b), the contact pressure (p) shown in
FIG. 6 was low and was, for example, approximately 25 MPa. In the
forging phase (c), the contact pressure (p) is essentially left at
this value. Alternatively, it can be increased to the
aforementioned 125 MPa, or preferably 100 MPa or even less.
[0093] The contact pressure (p) can be kept constant during the
forging phase (c). Alternatively, it can vary, for example rise or
fall in a ramp-like or step-like manner, or also fluctuate around a
constant or variable mean value. The forging phase (c) takes longer
than the grinding phase (b). The duration can be 1-4 seconds, for
example.
[0094] FIG. 5 shows the final state of the forging phase (c), in
which the workpieces (2, 3) are joined and form a connected joined
part (6), which can possibly have a ring-like bead (23) at the
joining zone (21). FIGS. 4 and 5 also illustrate the axial growth
and widening of the heating region (22) during conductive
heating.
[0095] At the beginning II of the forging phase (c), the electric
current (I) shown in FIG. 6 with solid lines is switched on, for
example, and results in the conductive heating.
[0096] In the variant with a preceding current pulse in the
grinding phase (b), it can also be increased significantly at the
start II of the forging phase (c).
[0097] The current (I) can be switched on, for example, in the
deceleration phase of the relative movement, with falling speed
(v), or when the contacting workpieces (2, 3) are at a standstill.
The electrical current (I) can be switched on immediately at
standstill or, if necessary, with an adjustable time delay.
[0098] The electrical current (I) remains switched on during the
forging phase (c). It can be constant during the forging phase (c),
in accordance with FIG. 6. Alternatively, it can vary. The
variations can be ramp-like or step-like, rising or falling, or
also fluctuating around a constant or variable mean value. Any
variations in the profile of the contact pressure (p) and the
current (I) can be adapted to each other.
[0099] The variations in the profile of the current (I) and
optionally the contact pressure (p) can be controlled and, if
necessary, adjusted by the controller as a function of the signals
or detected values of the detection device (25). In this way, for
example, the conductive heating can be adapted to the
transformation and phase behavior of materials, in particular
metals, in order, for example, to achieve a desired structure.
[0100] The plasticizing heating and joining of the workpieces (2,
3) subjected to contact pressure is completely or predominantly
caused by the conductive electrical heating in the forging phase
(c).
[0101] At the end of III of the forging phase (c), the forging
device (8) and the current source (16) are switched off. The
current (I) can be switched off at the same time as the contact
pressure (p), or shortly beforehand. The current (I) remains
switched on for at least the greater part of the duration of the
forging phase (c). The duration of the forging phase (c) is
determined by the duration of the contact pressure (p).
[0102] The workpieces (2, 3) or the joined part (6) joined in the
forging phase (c) according to FIG. 5 can be removed after the
workpiece holders (14, 15) have been opened. The workpiece holder
(14) can then be moved back into the starting or loading position
illustrated in FIG. 2 for repeated loading.
[0103] The friction/current joining process described above can be
expanded at the end and/or at the beginning. At the beginning, an
electrical preheating of the still-unjoined workpieces (2, 3) can
be added upstream. This can be done conductively or
inductively.
[0104] At the end, an electrical reheating process can be added.
This can also be done conductively or inductively. In the diagram
of FIG. 6, an extended switch-on duration of the current (I) is
shown in dashed lines for this purpose.
[0105] FIG. 7 shows a structural embodiment of the friction/current
joining apparatus (1) of FIG. 1. The friction/current joining
apparatus (1) has a friction device (7), a pressing device (8), a
machine frame (9) and a controllable and, optionally, adjustable
current source (16), along with current connections (17, 18) and a
current supply for applying the electric current for conductive
heating of the workpieces (2, 3) to the workpieces (2, 3) held in
the workpiece holders (14, 15). In FIG. 8, the current connections
(17, 18) and the current supply are shown separately.
[0106] FIG. 7 also shows a demagnetization device (32) with which
the components of the friction/current joining apparatus (1)
subjected to current and, if applicable, the workpieces (2, 3), in
particular the joined part (6), can be demagnetized.
[0107] In FIG. 7, the current source (16) is shown schematically.
The converter or converters (26) of the welding current source (16)
are not shown. FIG. 7 shows the arrangement of a transformer (27)
which is connected to the connection points (17, 18) via lines (30,
31). The transformer (27) is arranged in the vicinity and, for
example, above the workpieces (2, 3). It can be connected to, for
example, a slide-like adjusting device, and removed if
necessary.
[0108] The transformer (27) is connected to the current connections
(17, 18) via the aforementioned lines (30, 31). The lines (30, 31)
can be rigid or flexible. The line (31) from the transformer (27)
to the current connection (18) is movable, for example, and can
follow the axial and forging movement of the counter holder (13)
and its workpiece holder (15) along the process axis or machine
axis (10). This line (31) is designed, for example, as a bundle of
a plurality of flexible current cables laid in a bend and enclosed
in a cooling jacket. The line (30) leading from the transformer
(27) to the current connection (17) can be rigid and, for example,
in the form of current bars. Alternatively or additionally, it can
be designed to be flexible and in the form of current cables of the
aforementioned type.
[0109] In FIG. 7, two variants of electrodes (28, 28') on the
current connection (17) and on the moving workpiece holder (14)
assigned to the machine head (11) are shown in a drawing. In
practice, only one variant is usually used. FIG. 8 shows one of the
variants in a separate illustration.
[0110] FIG. 7 shows a design of the one or more electrodes (28) as
slip ring transmitters or brush transmitters. If necessary, the
electrodes (28) can transmit the current to the rotating workpiece
holder (14). The preferably multiple electrodes (28) are arranged
distributed on the outside on the cylindrical circumference of the
workpiece holder (14), and make contact with its shell. Within the
workpiece holder (14), there can be flexible line pieces which
establish a connection to the chuck jaws, which can be moved
radially, for example. The electrodes (28) can be movable to be
positioned against the workpiece holder (14).
[0111] FIGS. 7 and 8 also show an electrode variant with one or
more, preferably two, electrodes (28') which can be advanced
directly to the workpiece (2) held in the tool holder (14),
preferably when it is at a standstill, and brought into
current-conducting contact. These jaw-shaped electrodes (28') are
arranged in front of the tool holder (14). They are connected to
the transformer (27) via flexible lines (30).
[0112] FIG. 9 shows a further possible electrode variant. In this
case, the electrodes (28') are designed as axially movable jaws
which can be placed axially against the workpiece holder (14) in
the direction of the process axis (10) via an adjusting device (not
shown) and brought into current-conducting contact. The placement
can take place, for example, axially from the front or,
alternatively, from the front and rear in the case of a floating
infeed.
[0113] The electrodes or jaws (28') are designed, for example, as
edged ring portions, and can be brought into contact with the outer
end-face edge and the adjacent peripheral region of the workpiece
holder (14). This electrode shape is particularly suitable for
applying current when the workpiece holder (14) and the workpiece
(2) are at a standstill.
[0114] FIGS. 7 and 8 show a current connection (18) on the
workpiece holder (15) of the counter holder (13). The workpiece
holder (15) comprises, for example, multiple, in particular two,
movable clamping jaws which can be advanced to the workpiece (3),
which form electrodes (29) and are connected to the flexible line
(31).
[0115] FIG. 10 shows a variant of this in which the current
connection (18) is arranged on the workpiece (3), which is held by
the workpiece holder (15) on the counter holder (13). For this
purpose, one or more, in particular two, jaw-shaped electrodes
(29') are provided, which can be fed to the workpiece (3) with
their own adjusting drive, and brought into electrical contact. The
electrodes (29') are connected to the transformer (27) via
preferably flexible lines (31).
[0116] The degaussing device (32) can be designed in different
ways. In the case of electrical conductive heating of the contacted
workpieces (2, 3) by means of direct current, an electrical design
of the demagnetization device (32) that generates a demagnetization
current with reversed polarity is recommended. The current strength
of the demagnetizing current is sufficient to achieve the required
coercive force to demagnetize the exposed parts. The demagnetizing
current can be emitted in the form of one or more current pulses.
The demagnetization can take place during the forging phase (c), in
particular at the end thereof.
[0117] FIGS. 11 and 12 show exemplary circuit diagrams for such an
electrical demagnetization device (32).
[0118] In the variant of FIG. 11, the demagnetization device (32)
has its own converter (33) and its own transformer (34), which are
connected via lines to the current connections (17, 18) and deliver
a direct current. Its polarity is opposite to the polarity of the
conductive heating current, which is generated by means of the
converter (26) and the associated transformer (27). The current
connections (17, 18) can be located on the workpieces or on the
joined part (6) and/or on the workpiece holders (14, 15). The
converter (33) can be connected to the electrical network. It can
be controlled or adjusted independently. Adjustment is possible,
for example, by means of a detection device (not shown) which
detects the degree of magnetization of the affected components of
the friction/current joining apparatus (1), and optionally the
workpieces (2, 3) and/or the joined part (6).
[0119] FIG. 12 shows a further embodiment which functions with only
one converter (26), the demagnetization device (32) having its own
transformer (34) and a switch (35) on the primary side, for
example. The converter (26) for the electrical conductive heating
is connected to the transformer (27) and to the current connections
(17, 18) via the switch (35). The switch (35) switches over for
demagnetization and establishes an electrical connection between
the converter (26) and the other transformer (34), and the current
connections (17, 18) with reversed polarity.
[0120] In a variant not shown, the switch (35) can be arranged on
the secondary side. In this case, the converter (26) and
transformer (27) provided for the electrical conductive heating are
sufficient, the secondary switch being arranged between the
transformer (27) and the current connections (17, 18). For
demagnetization, it switches the polarity of the direct current
transmitted to the joined part (6).
[0121] FIGS. 11 and 12 also illustrate, in a schematic
representation, the exemplary design of transformers (27, 34) with
an integrated rectifier. The rectifier or rectifiers can
alternatively be designed and arranged differently.
[0122] In a further embodiment variant, which is not shown, the
demagnetization can take place by mechanical movement, in
particular vibration, by heat treatment, or alternatively by
alternating current--or also by a combination of different
procedures. In addition, there are further possibilities, for
example the temporary application of a permanent magnetic field or
the like.
[0123] Modifications of the embodiments shown and described are
possible in various ways. The features of the various embodiments
and the variants mentioned can be combined with each other, in
particular also interchanged.
[0124] While the present invention has been illustrated by a
description of various embodiments, and while these embodiments
have been described in considerable detail, it is not intended to
restrict or in any way limit the scope of the appended claims to
such de-tail. The various features shown and described herein may
be used alone or in any combination. Additional advantages and
modifications will readily appear to those skilled in the art. The
invention in its broader aspects is therefore not limited to the
specific details, representative apparatus and method, and
illustrative example shown and described. Accordingly, departures
may be made from such details without departing from the spirit and
scope of the general inventive concept.
LIST OF REFERENCE SIGNS
[0125] 1 friction/current joining apparatus [0126] 2 workpiece
[0127] 3 workpiece [0128] 4 joining surface, end face [0129] 5
joining surface, end face [0130] 6 joining part, joined part,
finished part [0131] 7 friction device [0132] 8 forging device
[0133] 9 machine frame [0134] 10 process axis, machine axis [0135]
11 machine head [0136] 12 drive, spindle drive [0137] 13 counter
holder [0138] 14 workpiece holder, chuck [0139] 15 workpiece
holder, chuck [0140] 16 current source [0141] 17 current connection
[0142] 18 current connection [0143] 19 forging drive, cylinder
[0144] 20 output element, piston rod [0145] 21 joining zone [0146]
22 heating region [0147] 23 bead [0148] 24 controller [0149] 25
detection device [0150] 26 converter [0151] 27 transformer [0152]
28 electrode, slip ring [0153] 28' electrode, jaw [0154] 29
electrode [0155] 29' electrode, jaw [0156] 30 line [0157] 31 line
[0158] 32 demagnetizing device [0159] 33 converter [0160] 34
transformer [0161] 35 switch [0162] P contact pressure [0163] v
speed [0164] I electric current [0165] a contacting phase [0166] b
grinding phase [0167] c forging phase
* * * * *